1. Field of the Invention
The present invention relates to a can feeding apparatus which can convey cans stably from a can filler to a can lid feeder and a can seamer in a canned food production line.
2. Description of the Prior Art
A layout of the heretofore known portion of the canned food production line associated with a can seamer, that is, an arrangement of the respective machines from a can feed conveyor upstream of the can seamer to an ejection turret, is shown in FIG. 14. In this arrangements, can bodies 1 filled by a can filler (not shown) are conveyed in the direction of arrow A by means of a can feed conveyor 3 and fed into a seaming turret 7. The can feed conveyor 3 slides the can bodies 1 at a fixed pitch along a guide 6 and upon a rail 5 by means of a finger-associated roller chain 4.
In the outer circumferential portion of the seaming turret 7 are provided a large number of semi-circular recesses 7a conformed to the can body 1, and the can bodies 1 are received in these recesses 7a. In addition, an opposed turret 8 having recesses 8a of the same shape as the recesses 7a is disposed contiguously to the seaming turret 7 so that the recess 7a and the recess 8a jointly hold a can body 1 at a proper position on a straight line F--F connecting the centers of both turrets.
The can bodies 1 and can lids 2 in the seaming turret 7 are seamed by means of a seaming roll (not shown). Subsequently, the seamed cans are carried out of the can seaming via an ejection turret 9. It is a matter of course that the above-mentioned filler, seaming turret 7, opposed turret 8, ejection turret 9 and can feed conveyor 3 are synchronously operated, and their relative positions, i.e. their phases, are also regulated constantly. In addition, reference numeral 10 designates a drive sprocket for the above-described finger-associated roller chain 4, and reference numeral 11 designates a gear box for driving the drive sprocket 10 synchronously with the seaming turret 7.
Now, the operation of the apparatus when the can bodies 1 are delivered from the can feed conveyor 3 to the seaming turret 7 will be explained with reference to FIG. 15. The rail 5 of the can feed conveyor 3 has an oblique terminal edge extending along a large circular arc, and a can lifter 12, which is a component of the seaming turret 7, is moved into the space at the terminal end of the rail 5. The upper surface of the can lifter 12 is flush with the upper surface of the rail 5 on the underside of the conveyor 3 and the can lifter 12 itself rotating at a high speed in the counterclockwise direction shown by arrow C. The can body 1 would travel straightly as guided along its side and bottom while being pushed by the finger 4a of the drive chain 4 of the conveyor 3, and while it is being transferred onto the incoming can lifter 12 of the seaming turret 7, it is received in the cylindrical space formed by the recess 7a of the seaming turret 7 and the recess 8a of the opposed turret 8 and is thereby centered with respect to a seaming heat (not shown).
While a can body 1 filled with liquid is pushed by the finger 4a of the drive chain 4 of the can feed conveyor 3 and enters into the recess 7a of the seaming turret 7, and when the can body 1 is about to be transferred from the rail 5 on the underside of the conveyor 3 onto the can lifter 12 rotating at a high speed in the counterclockwise direction, as shown by a white bold arrow D in FIG. 15, a frictional force caused by rotation in the counterclockwise direction is abruptly applied to the bottom of the can. Hence, the can is momentarily accelerated in the traveling direction and advances as leaving the finger 4a of the drive chain 4 (shown by the advanced state of a can body 1' depicted by a double-dot chain line).
Since the timing by which the can body 1 is received in the recesses of the turrets 7 and 8 has been set so as to conform to the case where the can body 1 is being pushed by the finger 4a of the drive chain 4, in the event that the can body 1 has been advanced after leaving the finger 4a, the can body 1 would strike against corners 7b and 8b of the seaming turret 7 and the opposed turret 8. Therefore, there is a possibility that the can body 1 will become unsteady resulting in the spilling of the liquid or scratches and depressions being formed in the can body 1. In particular, when changing the apparatus to cope with can bodies having a smaller diameter than those previously seamed, or in the case where the roundness of the can bodies is not sufficient and the width between the opposite rails of guide 6 is somewhat increased, there was a shortcoming in that the can body 1 would enter deeply into the space between the corners 7b and 8b and when the corners 7b and 8b confronted each other, the can body 1 was bitten therebetween and the can body would be depressed so much as to be damaged.
On the other hand, in case where can having different sizes are to be seamed, the replacement of parts such as the turret and the like, as well as an adjustment of the remaining parts are necessary. Of these requirements, only a phase adjustment of the can feed conveyor will be explained. FIG. 16 is a plan view of a portion of the apparatus at the time when the center of the recess 7a of the seaming turret 7, the center of the recess 8a of the opposed turret 8 and the center of the can body 1 coincide with the straight line F--F. If the can size is changed, e.g. if the apparatus set up to handle can body 1 is changed to handle the can body 1A and centering is effected, then a gap having a width f is produced between the outer circumference of the can body 1A and the finger 4a. Accordingly, in order to make the center of the new can body 1A coincide with the straight line F--F, it is necessary to displace the finger 4a by a distance f in the direction of arrow A.
The above-mentioned adjustment carried out in the prior art will not be explained with reference to FIG. 17. As shown in FIG. 17, the drive sprocket 10 is coupled to a drive flange 51 by means of a bolt 54 and a washer 55. The drive flange 51 is fixed to a drive shaft 52 rotating synchronously with the seaming turret 7. In addition, reference numerals 56 and 57 designate a latch bolt for the drive flange 51 and a washer. To effect the adjustment, the drive sprocket 10 is rotated relative to the drive flange 51 to displace the conveyor chain 9 by a distance f along a pitch line.
Referring again to FIG. 14, after the sprocket 10 has been released from the flange 51 by loosening the bolt 54, a dummy gauge having the same diameter as the can body 1A and made of a hard material is centered on the straight line F--F, the drive sprocket 10 is rotated so that the finger 4a of the drive chain 4 butts against the dummy gauge, and the bolt 54 is fastened to again fixe the drive sprocket 10 to the drive flange 51. A bolt hole 10a in the drive sprocket 10 is elongate so that the drive sprocket can be rotated within a suitable range. Although the fact that cans can be conveyed smoothly is confirmed by subsequently manually moving the can seamer, it is generally necessary to perform fine adjustments by repeating the above-mentioned operation several times.
As described above, a phase adjustment of a conveyor sprocket in the heretofore known apparatus requires a delicate adjustment of a drive sprocket and the like each time the apparatus is changed, to handle cans of a different size and consequently alot of labor and time were spent in carrying out the phase adjustment of the sprocket.
Next, one example of a known arrangement of the respective units of a seaming line, in which a can lid feeder is disposed in the middle of a can conveyor interposed between a can filler and a can seamer, will be explained with reference to FIG. 18. Such an arrangement is disclosed in Japanese Patent Application No. 3-131680 (1991). A can body 1 filled with liquid by a can filler (not shown) is conveyed by a can feed conveyor 3 in the direction of the arrow. As described previously, this can feed conveyor 3 consists of a finger-associated chain 4 having a function of pushing and conveying can bodies at a constant pitch along guides and beneath and extending along the side of the can bodies. In addition, reference numeral 106 designates a can lid feed mechanism, in which can lids 107 are fed one-by-one onto can lid guide plates 109 and 109a by a separate (not shown) at a timing matched with the traveling can bodies 1. The can lids are then placed on top of the traveling can bodies 1 by means of a can lid feed claw 105 b mounted to the tip of a tooth of a can lid feed turret 105. The can lids 107 thereafter drop from terminal end portions of the can lid guide plates 109 and 109a and are fitted to the can bodies 1 so as to cover the latter.
Now, the relative position between each can body 1 and the can lid 107 during the above-mentioned process will be described. In the can lid feed section, a traveling speed of a can body 1 moving on the can conveyor 3, and a circumferential speed of the pitch circle, i.e. a circle passing through the centers of circles coincident with the semicircular recesses of the can pockets 105a of the can lid feed turret 105, are set to be equal. Also, the same turret 105 and the can conveyor 3 are operated in phase with each other so that when a can body 1 traveling on the can conveyor 3 approaches the same turret 105, the can body 1 will enter a can pocket 105a of the same turret 105.
The teeth of the turret 105 are machined along cycloids, and hence the traveling can bodies 1 enter and leave the can pockets 105a of the same turret 105 without interfering with the teeth of the turret 105. When a can body 1 has entered a can pocket 105a of the same turret 105, as described above, the can lid 107 drops from the can lid guides 109 and 109a and is fitted to the can body 1 so as to cover the latter. It is to be noted that in FIG. 18, arrows E indicate the position where each can lid 107 is fitted to a can body 1 so as to cover it.
Next, an example of another heretofore known apparatus, in which a centering device is used at an inlet of a turret, will be described with reference to FIG. 19. Such an apparatus is disclosed in Japanese Utility Model Application No. 63-45564 (1988). In FIG. 19, reference numeral 101 designates a filler, numeral 119 designates a seamer, and numeral 112 designates an inlet guide. It is to be noted that FIG. 19 shows an example in which two can drum guide turrets 104, 104 are juxtaposed and switchable, and in which a can lid feeder 110 is disposed in line with the can conveyor 3 midway between the filler 101 and the seamer 119.
Now, the can drum guide turret 104 will be described in detail with reference to FIG. 21. Tip ends of teeth defining a can pocket 104a extend radially outward of a pitch circle, and the periphery of each portion 104b so extending has the shape of a cycloid. More specifically with reference to FIGS. 21 to 24, FIG. 21 shows a state in which a can body 1 is conveyed in the direction of arrow F by means of a chain having fingers 115 and is delivered into a can pocket 104a of the turret 104 rotating in the direction of arrow L as synchronized with the same chain. FIGS. 22, 23 and 24 respectively show cans 1a, 1b and 1c being sequentially conveyed.
At first, with reference to FIG. 21, a locus of the center of a can body 1 when the can is moved into a can pocket 104a is a cycloid G depicted by a dashed line. Hence, the portion of the tooth which would otherwise interfere with the can body 1 is omitted and the periphery thereof has the shape of a curve H depicted by a dashed line, whereby the periphery of the tip end of the tooth has the shape of a cycloid. It is to be noted that while the tip could be sharp, this tip can be cut into an appropriate length and can be rounded as shown in FIG. 20.
As the can body 1 is conveyed rightwards by the chain associated with the fingers 115, and once it has come to the position denoted by 1b in FIGS. 21 and 22, the can body 1 is held in position while in contact with the guides 112, 114, the can drum guide turret 104 and the finger 115 at points R and P on the front and rear of the can body and at points Q and S on the left and right sides of the can body. Under this restrained condition, the can body moves to the state shown in FIG. 23 and then, as shown at 1b in FIG. 24, the can is fed into the can pocket 104a of the can drum guide turret 104 under a stabilized condition.
In the heretofore known apparatus described above and illustrated in FIGS. 21 to 25, when the can bodies 1 are fed into the can pockets 104a of the turret 104 as conveyed by the chain, since the can bodies 1 are conveyed while in contact with the peripheral surfaces of the teeth of the turret 104 and the guides 112 and 114 before entering the can pockets 104a, even if the can bodies are filled with liquid, the liquid is prevented from spilling.
However, in the above-described apparatus in the prior art, the means for conveying can bodies 1 includes the fingers of a conveyor chain which push the can bodies 1 as guided by a rail beneath the can bodies and by guides on the both sides of the can bodies. In these cases, the rotational speed and phase of the can pockets 104a of the can drum guide turret 104 are matched with the speed and phase of the can bodies 1 pushed by the fingers 115. Hence, although the can bodies correctly enter the can pockets 104a of the can drum guide turret 104, if the pitch of the can bodies should vary due to an error with the chain, then the timing would deviate. Namely, as shown in FIG. 25, the fingers 115 could be located at positions shown by the fingers 115' depicted by double-dot chain lines. Hence, the can bodies 1b would also be positioned as depicted by double-dot chain lines, thus striking a tooth (T) of the can drum guide turret 104. In this case, the can body would be pushed in the direction of the white bold arrow, and would be depressed and damaged as pinched between the tooth (T) and the can guide 112 at position (S). Also, when there is a difference between the height of the can drum guide turret 104 and the height of the can guide, there is a problem in that a torque is applied to the can body due to the pushing force upon pinching the can body, resulting in a tilting or unsteady movement, whereby the liquid could spill out. Despite these problems, however, an error in the uniformity of the pitch of the chain and of that in the pitch of the can being conveyed by the fingers caused by the error must be tolerated to a certain extent.